Laing. — Observations on the Fucoideas. 307 



size, they are cut off from the surrounding tissue by a ring of 

 small cells. The third tissue consists of anastomosing filaments 

 which have no particular direction with regard to the axis of the 

 plant. 



Reproduction by zoogonidia, developed in sporangia,* closely 

 packed together on the lower portions of the frond. The 

 " clavate, inarticulate filaments" of the Handbook are probably 

 young sporangia. I have not as yet been able to see the 

 zoogonidia escape. It is worthy of notice that the sporangia are 

 developed in corresponding patches on both sides of the frond. 



Common, just below low water-mark. 



9. Macrocystis dubenii. 



Description in Hooker's " Handbook of New Zealand Flora " 

 (Generic:) " Eoot branching, giving off immensely long, slender, 

 simple stems, which bear leaves at the surface of the water. 

 Leaves formed by the continual splitting of a primary terminal 

 leaf, developed in secund order along the lengthening floating 

 stem, each lanceolate, serrate, ribless, undulate, with a pyriform- 

 oblong or sub-cylindric bladder at its base. Spores superficial 

 on submerged radical leaves, forming clouded sori, ellipsoid with 

 a hyaline coat, surrounded by densely-packed inarticulate para- 

 nemata." (Sp.) " Stems, 50 to perhaps 700 feet long or up- 

 wards. Fronds extremely variable in length and breadth, 2-4 

 feet long, 2-6 inches broad, ciliate-serrate." 



It is wrongly here stated that the stems are simple. They 

 branch dichotomously, but only immediately above the rhizoid. 

 The length of the stem .has been variously stated ; and it is 

 generaUy said to be the longest plant in the world. In Lyttelton 

 Harbour, however, it certainly does not attain a greater length 

 than 70 feet ; commonly it is from 20 to 30 feet long. In 

 structure the stem is very similar to that of Ecklonia. The 

 secretion canals are present, and originate in the stem, at some 

 distance below the apical leaf. In the " Transactions of the New 

 Zealand Institute," vol. xiv., p. 562, it is said : " Professor Parker 

 exhibited and made remarks upon sections of the stem of Macro- 

 cystis, showing sieve tubes like those of Cucurbita." This doubt- 

 less refers to the anastomosing cells of the central tissue, which 

 sometimes closely resemble the sieve tubes of Cucurbita, as 

 figured by Sachs. 



The bladders are formed by the central tissue ceasing to 

 grow, whilst the external tissues develope rapidly ; and, con- 

 sequently, the stem at this point swells outward, and at last tears 

 apart the filaments of the central tissue, which are left hanging 



*I am compelled to use the incorrect term " sporangia," as there is no 

 other English word which can he made to express the idea " mother cells of 

 the zoogonidia." 



